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Researchers at Harvard School of Engineering and Applied Sciences (SEAS) have developed a breakthrough metal-free flow battery technology that can store renewable energy at lower cost.

Backed by the US Department of Energy's Advanced Research Projects Agency-Energy (ARPA-E), the project is aimed at developing the innovative grid-scale battery.

Designed and tested in the laboratory of Michael J. Aziz, Gene and Tracy Sykes Professor of Materials and Energy Technologies at the Harvard SEAS, the new battery depends on electrochemistry of naturally abundant, small organic carbon-based molecules called 'quinones' to store renewable energy.

Roy Gordon, Thomas Cabot Professor of Chemistry and Professor of Materials Science, has led the work on the synthesis and chemical screening of molecules, while Alan Aspuru-Guzik, Professor of Chemistry and Chemical Biology, applied his molecular screening methods to determine the properties of more than 10,000 quinones to chose the best candidates for the battery.

Flow batteries, which store energy in chemical fluids contained in external tanks, feature two main components including the electrochemical conversion hardware and the chemical storage tanks as against the traditional batteries, in which the hardware and energy capacity are integrated in one unit.

The hardware enables the flow of fluids and sets the peak power capacity, and independently sized chemical storage tanks set the energy capacity, allowing 'economical' storage of larger amounts of energy in flow batteries than traditional batteries.

"Backed by the US Department of Energy's Advanced Research Projects Agency-Energy, the project is aimed at developing the innovative grid-scale battery."

Michael Aziz said, "Our studies indicate that one to two days' worth of storage is required for making solar and wind dispatchable through the electrical grid."

Team leader Aziz said that they will carry out further tests, optimise the flow battery system and then ultimately bring it toward a commercial scale.

Project collaborator Sustainable Innovations is likely to deploy demonstration versions of the organic flow battery contained in a unit by the end of the three-year development period.

In the demonstration project, electricity from the solar panels equipped on a commercial building's roof will either be supplied directly to the building or into the storage system for use when required.

Many engineers have been working on the flow battery technology to unlock a new method of economically storing the energy, but until now, such batteries have been based on expensive chemicals, increasing the energy storage costs.

Image: A prototype flow battery in Aziz's lab at Harvard School of Engineering and Applied Sciences. Photo: courtesy of Eliza Grinnell, SEAS Communications.